Wind slabs are lingering on north- and west-facing aspects but are gaining strength. A loose wet avalanche problem may develop if wind easers and solar radiation are intense. The weather is settled over the next 24 hours with light winds and fine periods. Showers possible later in the day.
Wind slabs are lingering on north- and west-facing aspects. Wind slab deposits are located near sheltering terrain features and catchments. Triggering these wind slabs is more likely on steep, unsupported slopes. The northern aspect of Tahurangi has had continued loading over the past few days. It's advisable to approach any freshly loaded slope with caution, especially those that are convex-shaped and positioned high in the path.
Loose wet avalanche activity will become possible if cooling winds ease and the sun makes an appearance. Cold wind-driven new snow deposits will react negatively to any rapid warming. Solar aspects, mostly north-facing, will be prone to structural breakdown of surface layers. Watch for signs of solar effect such as rollerball and pinwheel activity.
No natural or human-triggered avalanche activity has been reported or observed over the past 24 hours.
Light rime formation overnight in the southwest. Very little precipitation has affected the snowpack over the past 24 hours. Turoa received about 30-40 cm of new snow above 1600 metres during the last storm cycle. This new snow was paired with gale southerly or southeast winds. Wind slab deposits are over 100cm deep in the southern areas on northern- and west-facing aspects. These wind slab deposits are gaining strength. In the northwest, isolated pockets of wind slab also exist. The gale southerly winds have stripped exposed slopes, leaving a rain crust at the surface. Threshold is now about 1800 metres in the northwestern areas. Snow cover will exist on Mt Ngauruhoe and Mt Tongariro. Snow and ice are present on the Tongariro Alpine Crossing. Alpine skills and equipment are essential to hike this track. If doing the Tongariro Crossing, you will be traveling over snow and ice with exposure to start zones at threshold. Recommend alpine gear and take avalanche precautions. Threshold in the southwest remains at an elevation of about 1600 metres.
Friday the 21st of August is mainly fine, with some morning low cloud, then isolated showers developing in the afternoon. The winds are light westerly, tending northwest later. The freezing level is 2200 metres, lowering to 1900 metres for a time in the morning. High pressure builds over the country today, then retreats onto the North Island during Friday. Meanwhile, a strong north-westerly flow develops over the South Island on Friday, and a front approaches Fiordland late in the day.
Strong winds can strip exposed slopes, making the surfaces slick and icy. Numerous hazards, including exposed rocks and cliff bands, exist. It is recommended to carry an ice axe and crampons when venturing into the backcountry. Having strong alpine skills and competence is essential for navigating over slick surfaces, as the consequences can be severe.
Moderate
New Zealand Avalanche Advisory (NZ Mountain Safety Council)
